Process for desulphurizing alkyl phenols



Patented June 20, 1939 UNITED STATES PATENT OFFICE PROCESS FORDESULPHURIZING ALKYL PHENOLS pany, San Francisco, Calii'., a

Delaware corporation of No Drawing. Application November 22, 1937,

- Serial No. 175,876

11 Claims.

This is a continuation-in-part of our copending application Serial No.144,658, filed May 25,

1937, and relates to an improvement in the methd of purifying alkylphenols containing aromatic mercaptans i. e., thiophenols and otherorganic non-mercaptan sulphur compounds. More particularly it deals withan improved method for desulphurizing alkyl phenols recovered frompetroleum oils by highly efllcient extraction means.

In the above mentioned co-pending application Serial No. 144,658, wehave shown that in a order to recover the largest portion of alkylphenols from petroleum oils, methods of extraction must be employedwhich yield extracts containing besides the alkyl phenols highpercentages of impurities, notably neutral oils, carboxylic acids, andsulphur and nitrogen com pounds. Some of these impurities are removedfrom the alkyl phenols with extreme diillculty only, and the expensesdue to consumption of chemicals and losses of alkyl phenols are oftenexcessive.

We have further shown that by a process in which a series ofindividually known steps is carried out and combined in a certainmanner, good yields of commercially pure alkyl phenols, i. e., which aresufliciently pure to meet commercial requirements, are obtained at amuch lower cost than has been possible heretofore. This process consistsessentially of the following steps:

(1) Extracting a petroleum oil containing alkyl phenols, while in theliquid state, with an aqueous alkali metal hydroxide solution of anoriginal concentration of 35-50% under conditions to form two layers andseparating the layers:

(2) subjecting the aqueous layer to a prolonged steaming withsubstantially saturated steam to drive off certain impurities and toprecipitate a sludge which is separated, and continuing to steam untilno further sludge precipitates;

(3) carbonating the steamed clear liquid aqueous layer with carbondioxide to liberate alkyl phenols, thereby forming two layers, andseparating the layers;

(4) rapidly distilling the liberated alkyl phenols under vacuum;

(5) if desired, further purifying the distilled alkyl phenols byoxidation, preferably with air at a temperature between about 140-150 C.followed by redistillation, and the redistilled product may further beblown at about room temperature to remove possible foul odors.

The distillates resulting from Step 4 contain as their main impuritiessulphur compounds, largely in the form of aromatic mercaptans, i. e.,thiophenols, and the object of the subsequent oxidation step is mainlyto eliminate these thiophenols.

It is a purpose of the present invention to improve the above process,particularly the oxidation step, so that commercially pure alkyl phenolsof even lower contents of thiophenols and other sulphur compounds can behad, if possible, at no increased cost. In some instances where anexceptionally low sulphur content is required, consumption of treatingchemicals may, however, have to be raised.

One of the difliculties of our former procedure consisted of thenecessity of having to carry out the oxidation with air at relativelyhigh temperatures, because at lower temperatures the rate of oxidationof thiophenols to disulphides is too slow in, most cases. Withincreasing tem peratures the rate increases; however, at the same timeundesirable side reactions set in, some of which consume alkyl phenolsand lead to the formation of dehydrogenated products of unknowncomposition.

Furthermore it is sometimes diflicult, if not impossible, to remove bydistillation at least a portion of the disulphides from alkyl phenolmixtures, particularly if the latter has a long boiling range, becauserelatively low boiling thiophenols may form disulphides boiling within aboiling range of the higher boiling alkyl phenols. Moreover at therelatively high temperatures of distillation, even when distilling underhigh vacuum, aromatic disulphides may be reconverted to thiophenols.

Now we have discovered that the oxidation of thiophenols in the alkalinestate proceeds satisfactorily at about room temperature. At thistemperature undesirable reactions do not take place to a materialextent. With increasing temperature the rate of oxidation of thiophenolsto disulphides increases, but at the same time a reversal of thisreaction, namely reduction of disulphides to thiophenols at the expenseof alkyl phenols also accelerates. Therefore, temperatures substantiallyabove room temperature not only fail to give better conversions ofthiophenols to disulphides, but may result in material losses of alkylphenols.

We have found that at temperatures above about to C. the reversedreaction proceeds at such a rapid rate that for practical purposes nooxidation of thiophenols to disulphides takes place, and alkyl phenolsonly are attacked. Similarly, if an alkali alkyl phenolate solutioncontaining disulphides is heated to about 90 C, or higher, thiophenolsare reformed rapidly and alkyl phenols are oxidized even in the absenceof air. For these reasons we maintain during the oxidation andafterwards as long as disulphides are present temperatures below aboutto C. and preferably below about 50 C. At 50 C. or lower the reformationof thiophenols from disulphides is sufliciently slow so that oxidationof thiophenols to disulphides and sepa ration of the latter from thealkali alkyl phenolate solution can be achieved without appreciable lossof alkyl phenols.

In addition to enabling satisfactory oxidation with air without undueinterference from side reactions, when operating in the alkaline stateat about room temperature, this method has the further advantage ofmaking possible easy separation of the disulphides from the alkali alkylphenolate solution as will be described later.

Accordingly the present invention comprises the steps of effecting theoxidation of sulphur compounds and in particular thiophenols, conpendingapplication. By so doing no chemicals 7 in excess of those used in ourolder process are required, and yet after carbonation and vacuumdistillation of the liberated alkyl phenols a product is obtained whichhas a sulphur content considerably lower than that obtainable by airblowing the free alkyl phenols in the acid state after completed vacuumdistillation as was formerly done.

An alternative method which may have to be resorted to, where sulphurrequirements are exceedingly low, consists of redissolving the liberatedvacuum distilled alkyl phenol in a suitable alkaline liquid medium toproduce a phenolate solution, air blowing the latter at about roomtemperature, separating disulphides, and reacidifying the blown solutionto liberate the alkyl phenols.

If desired, both modifications may be combined, i. e., the alkylphenolate extract after being steamed and separated from precipitatedsludge is air blown, disulphides are separated, and the blown solutionis carbonated to liberate the alkyl phenols. The alkyl phenols arevacuum distilled, redissolved in a suitable alkaline medium and theresulting solution is again blown with air. Disulphides are separated,the blown solution is acidified and liberated phenols may beredistilled.

The entire extraction and treating process is as follows:

A petroleum .oil containing alkyl phenols, such as a cracked distillateboiling between about to 300 C. is extracted with an aqueous solution ofan alkali metal hydroxide.

The step of extracting the petroleum oil consists essentially oftreating the liquid oil with an amount of an aqueous. alkali metalhydroxide solution, preferably sodium or potassium hydroxide, of anoriginal concentration of 35-50%, which amount contains a quantity offree hydroxide only slightly in excess of that required to convertcaustic alkali solution of about 35-50% concentration a precipitation ofphenolates takes place, and upon further addition of a certain minimumcritical amount of alkyl phenols, which amount is less than thatrequired to consume all of the free alkali metal hydroxide, theprecipitated phenolates are redissolved in the aqueous phase. Thus byadding to an alkali metal hydroxide solution of the above strength theminimum critical amount of alkyl phenols required to form a singleaqueous phase of phenolates, a solution is obtained which containsbesides the phenolates considerable quantities of free alkali metalhydroxide. This critical amount varies considerably with theconcentration of the hydroxide and the type of alkyl phenols added. Forinstance, when using a mixture of alkyl phenols of an average molecularweight'of xylenols, the critical amount required to produce a singlephase would be as follows for aqueous sodium hydroxide solutions ofvarious concentrations:

Critical amount of alkyl phenols percent by weight of solution Originalconcentration of NaOH in caustic solution Per cent 35 cats.

The resulting phenolate solution containing free alkali metalhydroxideis the most effective extractant for alkyl phenols from hydrocarbonoils, if contacted with the oil in the proper proportion. The amount ofalkaline alkyl phenolate solution used to treat a given amount of oilcontaining alkyl phenols should be such that the amount of alkyl phenolsin the oil is sumcient to convert a portion only of the free alkalihydroxide to alkali phenolates, and the enriched phenolate solution thusproduced should preferably contain phenols after this extraction. Aportion of the phenolate solution is then withdrawn from circulation tobe treated as will be described hereinafter. The remainder of the alkylphenolate solution is mixed with'an amount of fresh caustic alkalisolution of 35-50% concentration sufficient to replace the amount ofalkali metal withdrawn before, and the resulting mixture containing freealkali is again contacted with fresh oil as described above.

While by this method of extraction substantially complete removal ofalkyl phenols from petroleum oil is accomplished, the alkyl phenols soextracted are highly contaminated with impurities. Besides alkylphenols, other substances are dissolved in the aqueous phenolatesolution, notably naphthenic and other carboxylic acids,

neutral hydrocarbons, sulphur compounds, n11 V trogen bases,' r'esinousbodies, etc.,-and in addition the-aqueous'solution may contain varying-"amounts of emulsifiedheavy tarry material, part,

of which may settle out, upon prolonged s'tanding Alkylphenolsliberated.from-the'untreated phenolate solution by' acidification-may contain lfl ormore .per cent of'neutral oil, sulphur in" excess..of 1%, andinit'rogen bases as high as 6 -to aprolonged.steamingpreferably at substantially normal pressures and withsubstantially saturated; steam. The use of highly; superheatedalmostimpossible to obtain by any subsequent treatment, or combination.of simple treatments, except by double use of alkali metal hydroxideextraction {and acidification as forinstance described-by Merrill in U.S. Patent 2,000,244, alkyl phenols of sufficient stability and purityvto meet even the most liberal commercial requirements. I

During the early stages of the steaming perio'd,

neutral oils; nitrogen bases, sulphur compounds and a small portion,amounting'to less than l of the alkyl phenols of relatively -l owuacidities are vaporized .and removed overhead. Steaming, however, mustbe continued for some timeafter the removal of the volatilizablecompounds has is recognized when the exhaust steam, upon con- 1densation, no, longer turns turbid. While steaming proceeds, sludge isbeing formed and precipitated,-.and when the phenolate solution is al-,lowed to rest, two-separate layers form, an aqueouslayer and aheaviersludge layer. fUpon continued steaming the amount of sludgeformed eventually "reaches a maximum, so that when i the sludge isseparated andjthe desludged aquepouslayer is further steamed, noadditional sludge is formed; The time of steamingrequired to reach thispoint of maximum sludge formation normally varies between about 4 and 16hours, alkyl phenolates derived from relatively lowboilingdistillateslnormally requiring shorter time for-complete steamingthan'alkylphenolates obtain'ed 'from heavier oils. a

: It, is absolutely essentialjthat steamingbecartion; I Whilethereactions responsiblefor 'the'for, ination disludgeiarenot quiteunderstood, it ap-1 ofrre'moving neutral oils which act as disp'ersersfor actual slud 'er i. e.-, sludge-which' 'ispresent which take placeduring the steaming after re-.

The, phenolate solution containing 2 neutral, basic "and;sulphurousimpurities is now subjected process. 'Unless it is carried farenough it isbeen substantially completed. This latter point j 'ried outto the-maximum; point of; sludge forma- I v commercially pure alkylphenols in +pe'ars -that its production is. due to a combination from,the beginning; and condensation'freactions the phenolate solution.

solution contains emulsified organic matter other than sludge, whichrefuses to separate: at this point; In such a case diluting thephenolate somovaljrof neutral oils-and lead to the formationof;-additional-sludg e, for convenience called herein gpotential" sludgef Apparently nitrogen" :bases' take actiYefpartQJin {thesecondensation'-- reactions iforr'nirig, high-"boiling 'compounds,- andalthough; a considerable portion of; the-nitrogenous. condenvsationproducts mayremain in the: alkalinesolu i ftio'n- -after steaming,th'e'y 'la-ter. form partof the 'ftarryiresldue'produced'in thesubsequent vacuuinulsnnauon of the liberated alkyl phenols.

'It" appears that considerable time is required to condense the nitrogenbases, and if. steaming is the unreacted portion thereof will gooverhead in -the subsequent vacuum distillation jointlywith I .the alkylphenols. 'Slnce nitrogen bases, -to-.- gether with sulphur compoundsarethe most harmful and obnoxious. impurities .in commercial alkylphenols, it is readily seen how importantv it is to conduct the steamingto the point of maximum sludge formation.

-' We'are aware that alkyl phenols have been pro'duc'edby extractingcoal tars with aqueous caust-ic alkali solution, blowing the extractwith 'steam,,liberating the phenols and distilling and 'blowing'samewith air. However, in contrast to the above, phenolate solutionsobtained from coal tar distillates wlth'alkali metal hydroxide solutionsof customary concentrations, which are generally much lower than thosehereinbefore described, do not produce sludge upon steaming, perhapsbecause phenolate solutions obtained with relatively weak .alkalihydroxide solutions are comparatively little contaminated with im- 1phenols in petroleum oils is usually below 5% and. more often about ..1%or below. Obviously more effective means of extraction must-be appliedto petroleum oils than to coal-tar distillates, and thegreater.efficlency of extraction is at least partly responsible for the greaterdimculties experienced in the subsequent refining of the alkyl phenols,impurities which are normally associated with petroleum being extractedas well.

Aside from the relative amounts of the respective impurities, it alsoappears that there are considerable diiferences regarding their nature.As pointed out before, in petroleum alkyl phenols a class of littleknown nitrogen bases constitutes the most harmful impurities, whichnitrogen compounds seem to be almost completely absent from coal tarphenols. For this reason theextent of the steaming just sufficient toremove neutral oils has proven adequate in the purification of coal tarphenols, but in the case of purification of petroleum phenols has metwith failure; and

longed .to. give time for the condensation reactions'described above itwas impossible'to obtain the simple manner proposed by us.

, When the steaming has progressed-so that up .on further steaming noadditional-"sludge is formed; the precipitated sludge is separated fromUsually the 'desludged lution with at least an equal volume ofwaterwillr eadily break the emulsion. We have found it very convenient as arule to dilute the solution gto about.10%. If this doesnot produce a complete. break of the'emu'lsion, resort may be-had fto centrifugation orfiltration'through a suitable too short. condensation remains incompleteand before our discovery that steaming must be pro- I 4 amass? mediumwhich is preferentially wetted by the organic matter.

The phenolate solution is now perfectly clear and of much lighter colorthan before steaming, since neutral oils capable of dissolving sludgehave been removed substantially quantitatively as well as mostsludge-forming compounds and a portion of the sulphur compounds. Thisclear phenolate solution may now be blown with air at temperaturesbetween about and 90 C. and preferably below 50 C., for instance atabout normal room temperatures. Attemperatures below 0 C. the rate ofconversion of thiophenols to disulphides is too low to be practical, andat temperatures above about 90 C. the reversion of disulphides tothiophenols proceeds at such a rate as to prevent accumulation ofdisulphides, and results'in losses of alkyl phenols, as has beendescribed hereinbefore.

The time required for blowing in the absence of catalysts may be of theorder of to 60 hours depending upon the exact temperature of blowing,the sulphur content of the alkyl phenols, the desired degree ofdesulphurization, etc. Oxidation catalysts may be added to acceleratethe rate of formation of disulphides. Suitable catalysts are, forinstance the metals, oxides and sulphides of copper, lead, manganese andferrous metals,

or mixtures thereof, in particular the nickel and lead sulphides.However, other known oxidation catalysts may also be used.

The disulphides formed in the oxidation are largely insoluble in thephenolate solution. They are compounds of high wetting powers forsilicates, metals and many other solids and consequently tend to adhereto them. They may be separated from the phenolate solution byconventional method such as settling, centrifuging, flltering through afilter bed of solids; or washing with a hydrocarbon solvent such asnaphtha, benzene, or other suitable organic liquid which is immisciblewith the phenolate solution and which does not extract phenols fromphenolate solutions to an appreciable extent, or by a combination ofthese methods. Frequently the disulphides appear as a finely dispersedsuspension, in which case settling and centrifuging are insuillcient andextremely vigorous agitation with a solvent or filtration through a bedof sand or the like may be necessary.

The separation of the disulphides is preferably carried out withoutsubstantially raising the temperature, because upon heating even in theacid state, but more so in the alkaline state, the aromatic disulphidestend to revert to their respective mercaptans. In this respect aromaticdisulphides differ considerably from aliphatic di- I sulphides whichnormally can be distilled without material decomposition. Thereforephenolate solutions containing separated and/or dissolved aromaticdisulphides should not be heated above about 90 C., and atemperaturebelow about 50 C. is preferably maintained before and during the removalof the latter.

The desulphurizedphenolate solution is now carbonated by introducinginto it carbon dioxide or a gas containing carbon dioxide such as fluegas, or lime kiln gas, etc. in an amount so that preferably theresulting aqueous solution contains about an equi-molar mixture ofcarbonate and bicarbonate. Since phenols are acids weaker than carbondioxide, they are liberated while the stronger carboxylic acids as wellas hydrogen sulphide, if present, remain in the aqueous solution asalkali metal salts. Together with the alkyl phenols, organichydrosulphides such as thio phenols and mercaptans not removed bysteaming, are liberated. The liberated alkyl phenols form a separatelayer and are removed from the resulting aqueous carbonate solution inwhich the carboxylic acids are retained. The alkyl phenols may be waterwashed, such a wash often lowering the sulphur content by about .2 to3%. If desired, the carboxylic acids may be liberated and recovered fromthe carbonated solution, for instance by treating same with a relativelystrong acid, such as sulphuric, sulphurous, hydrochloric, phosphoricacid, etc.

The separated alkyl phenols which usually conv tain a relatively smallamount of sulphur com- Pounds and more or less of dark colored resinousor tarry matter, are now subjected to a quick distillation, preferably aflash distillation under a reduced pressure, e. g., below about 25 mm.mercury. Since the resinous or tarry compounds associated with the crudealkyl phenols are thermally unstable and crack very readily, therebyforming both neutral oils and tar, distillation must proceed at thelowest practical temperature, preferably below 180 C. and at the highestrate possible. The resulting distillates are mixtures of alkyl phenolsof light colors, good color stabilities and very low sulphur contents.

As has been indicated hereinbefore instead of proceeding as described,the steps of blowing with air and separating disulphides may be carriedout after completed vacuum distillation. In this case the alkyl phenolswhich may or may not have had an air blowing treatment or redissolved inan alkaline liquid medium to form aliquld solution. We prefer to use anaqueous alkali metal hydroxide in which to dissolve the phenols,although other suitable bases such as various amino bases for instanceaqueous ammonia, alkyl amines, alkanol amines, alkylenediamines,aniline, aqueous quaternary ammonium bases may be used instead. Theresulting phenolate solution is then blown for several hours with air ata temperature preferably below about 50 C. such as room temperature, anddisulfldes are then separated by one of the methods described beforewhich may be applicable. The blown and desulphurized phenol- ,atesolution is carbonated to liberate the alkyl phenols and if desired thelatter may be redistilled.

The reductions in the sulphur content which can be had by our improvedprocess are well illustrated in the following examples:

A mixture of alkyl phenol which was produced in accordance with themethod of our co-pending application Serial No. 114,658, had a mercaptansulphur content of 1.5 prior to blowing with air at 140 to 150 C. Afterblowing for 10 hours at 145 C. and redistilling, under vacuum themercaptan sulphur content was 0.5%.

When, however, producing alkylphenols from the same source by the methodof this invention, according to which the alkyl phenolate extract wasblown following completed steaming and sludge separation, the mercaptansulphur content was reduced to .05%. If instead of air blowing theaqueous phenolate extract, the vacuum distillated phenols containing1.5% of mercaptan sulphur were redissolved in a 10% aqueous caustic sodaand the resulting phenolate solution was blown at room temperature for10 hours, the mercaptan sulphur content after separation of disulfldeswas of the order of .001 to .005%;' and if air blowing in alkalinesolution was employed twice,- namely before and after vacuumdistillation contents of mercaptan sulphur were well below .001%.

We claim as our invention:-

1. In the process of refining alkyl phenols containing aromaticmercaptans, the steps comprising blowing the alkyl phenols with air at atemperature between and 90 C. while in solution of an alkaline-reactingliquid medium stable under the conditions of the treatment, for a timesufllcient to convert mercaptides to disulphides which are largelyinsoluble in said solutions and form a separate phase, and removing theseparated disulphides from the solution while maintaining a temperaturebelow about 90 C.

2. In the process of refining alkyl phenols containing aromaticmercaptans, the steps comprising blowing the alkyl phenols with air at atemperature between 0 and 50 C. while in solution of analkaline-reacting liquid medium stable under the conditions of thetreatment, for a time sufllcient to convert mercaptides to disulphideswhich are largely insoluble in said solutions and form a separate phase,and removing the separated disulphides from the solution whilemaintaining a temperature below about 50 C.

3. In the process of refining alkyl phenols containing aromaticmercaptans, the steps comprising oxidizing the alkyl phenols while insolution of a liquid aqueous alkali metal hydroxide, by blowing samewith air at a temperature between 0 and 90 C., for a time sufilcient toconvert mercaptides to disulphides which are largely insoluble in saidsolutions and form a separate phase, and removing the separateddisulphides from the solution while maintaining a temperature belowabout 90 C.

4. Theprocess of claim 3 in which the oxidation is carried out in thepresence of an oxidation catalyst capable of accelerating the oxidationof mercaptans to disulphides.

5. In the process of refining alkyl phenols containing aromaticmercaptans, the steps comprising blowing the alkyl phenols with air at atemperature between 0 and 90 C. while in solution of analkaline-reacting liquid medium stable under the conditions of thetreatment, for a time suflicient to convert mercaptides to disulphideswhich are largely insoluble in said solutions and form a separate phase,and filtering the solution while maintaining a temperature below about90 C.

6. In the process of producing commercially pure alkyl phenols from apetroleum distillate containing same and aromatic mercaptans, comprisingextracting the distillate with a quantity of an aqueous alkali metalhydroxide solution 'of 35 to 50% concentration to form an alkali metalalkyl phenolate solution containing aromatic mercaptides, free alkalimetal hydroxide and a suflicient amount of alkyl phenols to preventprecipitation of the alkyl phenolates, steaming the resulting aqueousalkaline solution for a time sufficient to expel volatile impurities andto precipitate actual and potential sludges, separating the sludges fromthe solution of alkyl phenolates and mercaptides, carbonating thedesludged solution with an amount of carbon dioxide suflicient toliberate alkyl phenols and mercaptans, thereby forming two layers, analkyl phenol layer containing aromatic mercaptans and an aqueous layer,separating the layers, distilling the alkyl phenols and mercaptans underconditions to prevent substantial cracking, and

subjecting the alkyl phenols to an oxidation treatment to convertmercaptans to disulphides, the

improvement comprising effecting the oxidation by blowing the alkylphenols containing mercaptans with air at a temperature between 0 and 90C. while in solution of an alkaline-reacting liquid medium stable underthe conditions of the treatment, for a time sufficient to convertmercaptans to disulphides which are largely insoluble in said solutionsand form a separate phase, and removing the separated disulphides fromthe alkaline solution while maintaining a temperature below about 90 C.

7. In the process of producing commercially pure alkyl phenols from apetroleum distillate containing same and aromatic mercaptans, comprisingextracting the distillate with a quantity of an aqueous alkali metalhydroxide solution of 35 to 50% concentration to form an alkali metalalkyl phenolate solution containing aromatic mercaptides, free alkalimetal hydroxide and a suflicient amount of alkyl phenols to preventprecipitation of the alkyl phenolates, steaming the resulting aqueousalkaline solution for a time suflicient to expel volatile impurities andto precipitate actual and potential sludges, separating the sludges fromthe solution of alkyl phenolates and mercaptides, carbonating thedesludged solution with an amount of carbon dioxide sufficient toliberate alkyl phenols and mercaptans, thereby forming two layers, analkyl phenol layer containing aromatic mercaptans and an aqueous layer,separating the layers, distilling the alkyl phenols and mercaptans underconditions to prevent substantial cracking, and subjecting the distilledmixture to an oxidation treatment to convert mercaptans to disulphides,the improvement comprising redissolving the distilled mixture in aliquid alkali reacting medium stable under the conditions of thetreatment, to produce an alkyl phenolate and mercaptide solution,blowing the solution with air at a temperature between 0 and 90 0., fora time sumcient to convert mercaptides to disulphides which are largelyinsoluble in said solutions and form a separate phase, and removing theseparated disulphides from the alkaline solution while maintaining atemperature below about 90 C.

8. In the process of refining alkyl phenols containing aromaticmercaptans, the steps comprising blowing the alkyl phenols with air at atemperature between 0 and 90 C. while'in solution of analkaline-reacting liquid medium stable under the conditions of thetreatment, for a time sufiicient to convert mercaptides to disulphideswhich are largely insoluble in said solution and form a separate phase,and extracting the resulting mixture with an organic preferentialsolvent for disulphides which is immiscible with the solution to removedisulphides, while maintaining a temperature below about 90 C.

9. In the process of refining alkyl phenols containing aromaticmercaptans, the step comprising blowing the alkyl phenols with air at atemperature between 0 and 90 C. while in-solution of analkaline-reacting liquid medium stable under the conditions of thetreatment, for atime sufiicient to convert mercaptides to disulphideswhich are largely insoluble in said solution and form a separate phase,and extracting the resulting mixture with a hydrocarbon solvent toremove disulphides, while maintaining a temperature below about 90 C.

10. In the process of refining alkyl phenols containing aromaticmercaptans, the step comprising blowing the alkyl phenols with air at ateml perature between 0 and 90 C. while in solution an alkali metalphenolate solution containing mercaptides and volatile impurities,steaming said phenolate solution to expel said volatile impurities,contacting the steamed solution with air at a temperature between 0 and90 C. for a time sufllcient to convert at least a portion of saidmercaptides to disulphides which are largely insoluble in said phenolatesolution and form a separate phase, and removing the separateddisulphides from the phenolate solution while maintaining a temperaturebelow about 90 C.

WALTER J. HUND.

SAMUEL BENSON THOMAS. DANIEL B LUTEN, JR.

